The present invention relates to a tension adjustment device, and more particularly to a tension adjustment device for a chain saw. The tension adjustment device has a driving disk with two diametrically oppositely formed arcuate tracks formed thereon and a driven plate securely connected to the chain saw and having multiple bosses evenly and horizontally distributed on the driven plate. The two arcuate tracks are alternately received between two adjacent bosses such that when the driving disk rotates, the driven plate is moved linearly, which results in the adjustment of the tension of the chain saw.
With reference to FIG. 5, a conventional tension adjustment device for a chain saw as disclosed in U.S. Pat. No. 5,491,889 has an adjusting ring A, a dust-proof cap B with a hole B2 and a projection B3, a driving disk C with a central hole C1 and an arcuate channel C2, a driven plate E with a boss E1 received in the arcuate channel C2 and two positioning bosses E2, a guide F with two positioning holes F2 corresponding to the two positioning bosses E2 and a cutout F3 and a base G with a threaded bolt G2 and a guide pole G3 both received in the cutout F3. When the adjusting ring A rotates, the driving disk C rotates simultaneously with the adjusting ring A. Because the boss E1 is received in the arcuate channel C2, the driven plate E is moved as well as the guide F, which leads to the adjustment to the tension of the chain saw (not shown).
The adjustment to the tension of the chain saw is based on the engagement between the boss E1 and the arcuate channel C2. Therefore, when an adjustment is required, the shear is focus on the boss E1 and thus the boss E1 is easily worn and damaged.
To overcome the shortcomings, the present invention intends to provide an improved tension adjusting device to mitigate or obviate the aforementioned problems.
The primary objective of the invention is to provide an improved tension adjusting device having a driving disk with two diametrically oppositely formed arcuate tracks formed thereon and a driven plate securely connected to the chain saw and having multiple bosses evenly and horizontally distributed on the driven plate. The two arcuate tracks are alternately received between two adjacent bosses such that when the driving disk rotates, the driven plate is moved linearly, which results in the adjustment of the tension of the chain saw.
Another objective of the invention is to provide an adjusting member with an adjusting knob received therein and multiple first teeth formed on a bottom face thereof and a driven disk with multiple second teeth corresponding to the first teeth and securely formed with the driving disk, such that the rotation of the adjusting plate drives the rotation of the driven disk and thus the movement of the driven plate is moved and adjustment to the tension of the chain saw is accomplished.
Other objects, advantages and novel features of the invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings.